The invention relates to an articulated prosthesis for a lower limb and more particularly to an articulated prosthesis having knee and ankle joints which act in synchronism.
Lower limb prostheses include a thigh-piece connected for vertical rotation with respect to the lower part of the prosthesis by means of a horizontal pin positioned to intersect the vertical bearing axis of the prosthesis. The lower end of the thigh-piece has a knee with an abutting element for controlling the lower part of the limb to prevent unnatural rotation. Such a structure is relatively unstable in supporting the weight of the user's body due to the fact that the pin of the knee joint intersects the bearing axis of the prosthesis with consequent unforseen and uncontrolled rotation of the joint.
In addition to the above problems, the foot in such prostheses is connected for vertical rotation to the top part of the prosthesis by means of a horizontal pin with an elastic means in the heel acting in opposition to an abutment provided in the forward part of the foot. This abutment prevents the toe of the foot from rotating upward when the foot rests on the ground while bringing the other leg forward.
Since the ankle joint is independent of the knee joint, while the prosthesis is brought forward, the toe of the foot is rotated toward the ground, so that the user must raise himself up on the toe of the other foot in order to clear the downward pointing toe of the prosthesis.